Because Spanish doesn't work that way. Direct and indirect objects are constructed differently to English. The pronouns for DOs and IOs do look like reflexive pronouns but you have to get used to that.

I understand that "mandar" is similar to the English word "mandate" and would be used for sending an order, command or instruction (which may or may not be in writing). For example: "The doctor says Luis has cracked a bone in his ankle. Please excuse him from games for the next two weeks." --- "El doctor dice que Luis se agrietó un hueso en el tobillo. Por favor discúlpelo de los juegos durante las próximas dos semanas."